A wireless mesh network may have multiple entry/exit points, or portals, to a LAN. In some cases, a wireless mesh network may have multiple portals connecting to a single local area network (LAN) segment, or to several segments bridged together. Such a situation creates a networking problem. For example, the mesh network should appear as a single loop-free segment, to an 802.1D Spanning Tree Protocol (STP). If multiple portals connect back to the same LAN, and traffic is allowed to flow across them, a loop is created within the network. Traffic could leave the mesh network by one portal, cross the LAN, and reenter the mesh at the other portal. Traffic could also leave the LAN by one portal, cross the mesh network, and reenter the LAN at the other portal.
A common approach to a mesh network with multiple portals is to elect one of those portals, e.g., using some measure of bridge port priority, and to disable the others. This approach creates problems of its own. For example, if the single active portal loses its connection to the LAN, is powered down, or is blocked for any reason, the entire mesh loses its connection to the LAN until another portal is enabled. Also, using a single portal, in a configuration where multiple portals exist, creates an artificial bottleneck in traffic flow.